1. Field of the Invention
The present invention relates to agricultural harvesters such as combines, and, more particularly, to height control systems for headers on such harvesters.
2. Description of the Related Art
An agricultural harvester known as a “combine” is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating and cleaning. A combine includes a header which removes the crop from a field, and a feeder housing which transports the crop matter into a threshing rotor. The threshing rotor rotates within a perforated housing, which may be in the form of adjustable concaves and performs a threshing operation on the crop to remove the grain. Once the grain is threshed it falls through perforations in the concaves onto a grain pan. From the grain pan the grain is cleaned using a cleaning system, and is then transported to a grain tank onboard the combine. A cleaning fan blows air through the sieves to discharge chaff and other debris toward the rear of the combine. Non-grain crop material, such as straw, from the threshing section proceeds through a residue system, which may utilize a straw chopper to process the non-grain material and direct it out the rear of the combine. When the grain tank becomes full, the combine is positioned adjacent to a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
The header is typically controlled with a header height control system to maintain the header at a predetermined distance relative to the ground. In the case of a cutting platform type header, sensors may be incorporated into the skid plates below the header to control the height of the header relative to the ground. It is also known to use a non-contact type sensor which can sense the crop canopy or the ground below the crop canopy.
What is needed in the art is a header height control system with improved header height control capabilities.